Substances found in food and wine may be able to extend human life, according to new scientific research.

Scientists in the United States found that the substances - called polyphenols - can prolong the life of yeast cells significantly.They seem to work inside human cells too.

The best known polyphenol is found in red wine

Polyphenols are produced by many plants - perhaps the best known is resveratrol, found in red wine.

Scientists have been interested in them for a long time because they seem to reduce a person's chances of developing heart disease and cancer.

Now researchers at Harvard University have discovered that the chemicals can prolong the life of yeast by about 70%.

They do this by a mechanism which was previously unknown, by increasing production of enzymes called sirtuins.

Anti-ageing pill

The researchers also found that resveratrol increases sirtuin production in human cells in the lab; and, most compellingly, that it appears to prolong the life of flies and worms.

"Everyone's been interested in the polyphenols because of their anti-oxidant properties," said Dr Konrad Howitz, one of the team, and director of molecular biology at BIOMOL, a research company also involved in the study.

"But this mechanism with the sirtuins is new and I guess people are going to go back to the epidemiological data on heart disease and cancer and figure out how much is down to the anti-oxidant mechanism and how much to the sirtuins."

It is too early to conclude that the researchers have found an elixir of human life - further work is needed, and the first step is to see if resveratrol can make mice live longer.

That experiment is scheduled to start in a few months' time, and should give results in less than a year.

If polyphenols do give mice extra life, and if that extra life is healthy, the stage will then be set for human trials of something which scientists have dreamed of for centuries - a pill or potion to make us live longer.